James Webb: the new image of a newborn star – 11/05/2023 – Science

Imagine if you could go back in time 4.6 billion years and take a photograph of the Sun as it was rising. What would it be like?

Well, you can get an idea with this new image captured by the James Webb Space Telescope (JWST).

Near the center of this object, called HH212, a star is being born that is probably no more than 50,000 years old.

The scene would have been very similar when the Sun was a similar age.

In fact, you can’t see the protostar’s glow because it is hidden in a dense, rotating disk of gas and dust.

All you see are reddish-pink jets shooting in opposite polar directions.

HH212 is located in Orion, close to the three bright stars that form the “belt” of the mythical hunter that gives the constellation its name.

The distance from Earth is about 1,300 light years.

Physics suggests that these powerful gas emissions are the means by which the nascent star regulates its emergence.

“As the ball of gas mass at the center contracts, it spins. But if it spins too fast, it pulls apart, so something has to give up the angular momentum,” explained Professor Mark McCaughrean, the Agency’s scientific advisor. European Space Agency (ESA, for its acronym in English).

“We think it’s jets and emissions. We think that as all the material contracts, the magnetic fields come together and then some of the material coming through the disk is captured in magnetic fields and ejected through the poles. That’s why we call these bipolar structures,” the scientist told the BBC.

The reddish-pink color denotes the presence of molecular hydrogen. They are two hydrogen atoms joined together (just like the “HH” in the name of the protostar).

Shock waves move through the emissions, energizing them and making them shine brightly in this Webb image, which was captured predominantly at the infrared wavelength of 2.12 microns (that’s the second part of the protostar’s name).

The image of HH212 was captured by JWST’s near-infrared camera (NIRCam).

The protostar itself cannot be seen because it is covered by a dense disk of gas and dust, as mentioned above. There are a few mature stars in the field of view, but most of the points of light are very distant galaxies.

In the recorded image, it is possible to see the jets on the left and right and the bright nodes in each of them.

The structures are remarkably symmetrical… except that there appears to be an additional, albeit very confusing, impact arc to the right.

In fact, there is probably a complementary shock arc on the other side.

There are certainly hints of this in a larger version of this Webb image. It turns out that the density of gas and dust in space in that direction is thinner and so there is less material and the shock structure appears much more diffuse.

Astronomers have been studying HH212 for 30 years, taking photos every now and then to see how it has changed.

As expected with the Webb super telescope, its new view is 10 times sharper than anything that has come before and will allow scientists to delve deeper into the processes that drive star formation.

An interesting feature is to gather the entire image record to make a movie, to see how the elements in the jet structures change over time.

Repeated observations mean that the speed at which these elements move can also be measured: 100 km per second or more.

In a way, I imagined HH to mean molecular hydrogen, and that fits perfectly. But in reality, the acronym comes from Herbig-Haro, in honor of George Herbig and Guillermo Haro, who carried out pioneering work on this type of objects in the 1940s and 1950s.

Without a doubt, both would be surprised by James Webb’s capabilities. Not only because of the clarity of the image that it can achieve with its 6.5 m primary mirror, but also because of the range of colors that its instruments can detect, which makes the telescope so special.

“As we said, the main wavelength for looking at these things — impacted molecular hydrogen — is 2.12 microns, or about four times longer than the visible average. But for the first time, we now have a good picture of colors of this particular object because we can observe it at other wavelengths that simply can’t be seen by ground-based telescopes. And that will help us understand what’s really going on in the jets,” said Professor McCaughrean.

James Webb was expected to be transformative in many fields of astronomy, and the study of Herbig-Haro objects definitely benefited.

This object, located in the constellation Perseus, is even younger, also just thousands of years old. It’s curious to think that the Sun started out like this.